The Diet Debate: Mediterranean, Low-Fat, or Low-Carb?

We are often challenged to provide evidence-based advice to patients who seek to lose weight. To address the need for more information, investigators in Israel randomized 322 moderately obese adults (mean body-mass index, 31 kg/m²; mean age, 51; 86% men) to a low-fat, restricted-calorie diet; a Mediterranean, restricted-calorie diet; or a low-carbohydrate, non–restricted-calorie diet. The study was supported in part by the Dr. Robert C. and Veronica Atkins Foundation. Participants were weighed each month, and their adherence to the diets was validated by a food-frequency questionnaire.

Diet adherence overall was 85% at 24 months (best for the low-fat diet and worst for the low-carbohydrate diet [see Table 1]; P=0.04). All three diets resulted in a reduction in caloric intake at 24 months. Peak weight loss occurred within 6 months.

Weight loss at 24 months was significantly greater in the low-carbohydrate and Mediterranean-diet groups than in the low-fat group. All groups showed reductions in mean waist circumference and blood pressure, but the between-group differences were not statistically significant. Mean HDL levels increased in all groups, with the greatest increase in the low-carbohydrate group. Mean triglyceride levels declined the most in the low-carbohydrate group. Mean LDL levels did not change significantly in any group. C-reactive protein levels declined in only the Mediterranean-diet and low-carbohydrate groups.